Pole piece, preparation method and application thereof

Abstract

The invention provides a pole piece, a preparation method and application thereof. The pole piece comprises a current collector and an active material layer compounded on the surface of the current collector, the active material layer has a porous structure, and the porous structure is filled with porous particles. The porous structure of the active material layer is filled with the porous particles, so that the porous structure has an electrolyte storage effect, the dynamic performance of the electrode plate can be improved, the stability of the structure can be kept in the circulation and storage process by means of the porous particles, and the performance of the electrode plate is improved. The problems of deformation and collapse of the porous structure in the charging and discharging process of the electrode plate are solved.

Description

Technical Field

[0001] The present application relates to the technical field of lithium-ion batteries, and particularly to an electrode sheet, a preparation method thereof, and an application thereof. Background Art

[0002] With the development of the new energy industry in recent years, new energy vehicles have become the leading direction of the electrification transformation and development of the automotive industry, and the innovation and progress of new energy battery technology are one of the important development directions. At present, the iteration of lithium battery technology has reached a bottleneck, and there are significant contradictions in both high energy density and fast charging performance. Battery technology with both high energy density and fast charging performance is expected to become an important development direction of future battery technology, bringing huge market opportunities to related enterprises.

[0003] In the field of lithium-ion batteries, in order to design and manufacture battery cells with higher energy density, the coating weight of the electrode active material and the compaction density of the electrode active material are often increased, and the number of parallel electrode layers is reduced by reducing the amount of foil used. However, electrodes designed with high coating weight have a large polarization impedance during high-rate charge and discharge processes, resulting in deteriorated charge and discharge kinetics and prone to lithium plating problems, posing a significant safety hazard during the long-term use of battery cells.

[0004] Based on the above considerations, in order to improve the fast charging performance of thick electrodes, the prior art provides a surface porous electrode. The micropores on the electrode surface can significantly increase the specific surface area, electrolyte wettability, and liquid retention capacity of the thick electrode. However, the current designs of creating pores on the electrode surface do not consider the problems of pore structure deformation or collapse caused by the repeated "expansion - contraction" of the electrode during the cycling and storage of the battery cell.

[0005] Therefore, there is an urgent need to provide an electrode sheet, a preparation method thereof, and an application thereof to solve the above-mentioned technical problems. Summary of the Invention

[0006] Based on this, to overcome the defects of the prior art, the present application provides an electrode sheet, a preparation method thereof, and an application thereof. By filling porous particles in the porous structure of the active material layer, the stability of the porous structure during charge and discharge use is maintained, and at the same time, the wettability of the electrode sheet to the electrolyte can be improved, further enhancing the kinetic performance of the high coating weight electrode.

[0007] According to a first aspect of the present application, the present application provides an electrode sheet, comprising: a current collector and an active material layer composite on the surface of the current collector; the active material layer has a porous structure, and porous particles are filled in the porous structure.

[0008] By adopting the above technical solution, aiming at the drawbacks in pore formation of the electrode plate in the prior art, namely the problem of insufficient stability of the pore structure, the present application fills porous particles in the porous structure of the active material layer. By using the porous particles, the stability of the porous structure during charge and discharge is maintained, the risks of deformation and collapse of the porous structure during the charge and discharge process of the electrode plate are solved, and at the same time, the wettability of the electrode plate to the electrolyte can be improved, further enhancing the kinetic performance of the high coating weight electrode. Without deteriorating the kinetic performance, the occurrence of side reactions is significantly reduced.

[0009] As a preferred embodiment, the pore diameter R1 of the porous structure is 10 - 500 μm; the pore spacing L1 of the porous structure is 0.01 - 5 mm;

[0010] Further, the pore diameter R1 of the porous structure is 15 - 100 μm;

[0011] Further, the pore spacing L1 of the porous structure is 0.05 - 2 mm.

[0012] By adopting the above technical solution, setting the pore diameter and pore spacing of the porous structure within the corresponding ranges can improve the kinetic effect of the electrode plate. If the pore diameter and pore spacing are set too small, the kinetic improvement effect is poor; if the pore diameter and pore spacing are set too large, the active material is likely to fall off and the electrode plate is likely to deform.

[0013] As a preferred embodiment, the relationship between the pore depth H1 of the porous structure and the thickness H2 of the single-sided active material layer is expressed as follows:

[0014]

[0015] In the formula, the parameter α is a coefficient related to the intrinsic properties of the active material, and its value is between 0.05 and 0.9; C1 is the maximum rate during the battery charging process, and C2 is the maximum rate during the battery discharging process.

[0016] By adopting the above technical solution, adopting the relationship between the pore depth H1 of the above porous structure and the thickness H2 of the single-sided active material layer can improve the kinetics of the electrode plate to the required design.

[0017] As a preferred embodiment, the relationship between the total opening area S1 of the porous structure and the surface area S2 of the single-sided active material layer is expressed as follows:

[0018]

[0019] By adopting the above technical solution, if the total open area S1 of the porous structure accounts for too small a proportion, the improvement effect is poor; if the total open area S1 of the porous structure accounts for too large a proportion, the long-term cycling performance will be affected and the stability of the active material is poor. Therefore, by adopting the relationship between the total open area S1 of the above porous structure and the surface area S2 of the single-sided active material layer, the kinetics of the electrode sheet can be improved to the required design.

[0020] As a preferred embodiment, the porous particles are selected from one or more combinations of porous alumina, porous silica, porous silicate, porous ceramic, and porous metal oxide.

[0021] By adopting the above technical solution, the porous particles are highly conductive ionic porous materials, selected from one or more combinations of porous alumina, porous silica, porous silicate, porous ceramic, and porous metal oxide. The highly conductive ionic porous materials have small impedance and good wettability to the electrolyte, can penetrate into the pores, which is beneficial to lithium ion transport; and the porous particles are rigid ions with a certain strength, can maintain the stability of the pore structure and will not be melted by the solvent.

[0022] As a preferred embodiment, the average diameter of the porous particles is 0.5 - 5 μm; pores are provided inside the porous particles, and the average diameter of the pores is 1 - 60 nm; further, the average diameter of the pores is 1 - 40 nm.

[0023] By adopting the above technical solution, if the pores inside the porous particles are too small, it is not conducive to lithium ion transport and lithium ions cannot pass through the inside of the porous particles; if the pores inside the porous particles are too large, it is easy to adsorb too many impurities. Therefore, the average diameter of the porous particles and the average diameter of the pores are set within a suitable range.

[0024] According to the second aspect of the present application, the present application also provides a method for preparing the above-mentioned electrode sheet, including the following steps:

[0025] Prepare the negative electrode active material slurry, coat the prepared negative electrode active material slurry on the surface of the negative electrode current collector, and dry it to prepare a negative electrode sheet, and then roll it;

[0026] Prepare the positive electrode active material slurry, coat the prepared positive electrode active material slurry on the surface of the positive electrode current collector, and dry it to prepare a positive electrode sheet, and then roll it;

[0027] Perform a punching process on the prepared negative electrode sheet and positive electrode sheet to form the negative electrode sheet and positive electrode sheet with a porous structure; wherein, the punching process can adopt, for example, laser scribing and mechanical hole making or a combination of both;

[0028] Fill the porous particle slurry into the porous structures of the negative electrode sheet and the positive electrode sheet;

[0029] Bake the negative electrode sheet and the positive electrode sheet to obtain an electrode sheet filled with porous particles.

[0030] As a preferred embodiment, the preparation of the negative electrode active material slurry includes:

[0031] Add the first negative electrode active material, the second negative electrode active material, the first conductive agent, the second conductive agent, the first binder, and the first dispersant according to a mass ratio of (90 - 98):(0 - 5):(0.1 - 1.6):(0.1 - 1):(0.5 - 2):(0.7 - 2) to water and stir evenly.

[0032] By adopting the above technical solution, the above ratios and the blending of the negative electrode active material and the conductive agent in this application can be flexibly adjusted according to the battery type and performance requirements to achieve the best battery performance.

[0033] As a preferred embodiment, the preparation of the positive electrode active material slurry includes:

[0034] Add the first positive electrode active material, the second positive electrode active material, the first conductive agent, the second conductive agent, and the first binder according to a mass ratio of (90 - 98):(0 - 5):(0.1 - 1.6):(0.1 - 1.6):(0.1 - 2) to N-methylpyrrolidone and stir evenly.

[0035] By adopting the above technical solution, the above ratios and the blending of the positive electrode active material and the conductive agent in this application can be flexibly adjusted according to the battery type and performance requirements to achieve the best battery performance.

[0036] As a preferred embodiment, the first negative electrode active material is at least one of graphite and hard carbon materials;

[0037] The second negative electrode active material is one or two combinations of silicon-carbon negative electrode materials and silicon-oxygen negative electrode materials;

[0038] The first positive electrode active material and the second positive electrode active material are one or more of lithium iron phosphate, lithium manganese iron phosphate, lithium cobalt oxide, lithium manganese oxide, lithium nickel cobalt manganese oxide, and lithium nickel cobalt aluminum oxide;

[0039] The first conductive agent and the second conductive agent are one or more of acetylene black, conductive carbon black, carbon nanotubes, and graphene;

[0040] The first binder is one or more of polyvinylidene fluoride, polyacrylic acid, and styrene-butadiene rubber;

[0041] The first dispersant is one or more of sodium carboxymethyl cellulose and lithium carboxymethyl cellulose.

[0042] Compared with the prior art, the present application has the following beneficial effects:

[0043] The present application discloses a pole piece, a preparation method and an application thereof. For an electrode designed with a high coating weight, the polarization impedance during high-rate charge and discharge is relatively large, resulting in the deterioration of charge and discharge kinetics and the easy occurrence of lithium deposition problems, which poses a significant potential safety hazard during the long-term use of a battery cell. By combining pole piece pore formation and optimization of the pore structure design, the pore formation on the surface of the pole piece can significantly increase the porosity of the electrode and improve the kinetic performance of the electrode. However, with the increase in the specific surface area of the electrode, during high-temperature storage, the negative active material is more likely to undergo side reactions with the electrolyte, leading to the deterioration of the high-temperature storage performance of the battery. In addition, the design of pore formation on the electrode surface is too complex, without considering the feasibility of industrial production. At the same time, it does not consider the problem of deformation or collapse of the pore structure caused by the repeated "expansion - contraction" of the electrode during the cycle and storage of the battery cell. Therefore, in the present application, by means of porous particles, the porous particles are filled into the porous structure of the active material layer. Without deteriorating the kinetic performance, the occurrence of side reactions is significantly reduced. And by filling the porous particles into the porous structure of the active material layer, the stability of the porous structure during charge and discharge is maintained through the use of the porous particles, while improving the wetting of the electrode pole piece with the electrolyte, further enhancing the kinetic performance of the high-coating-weight electrode. This method of the present application does not require significant changes to the existing production line and process, has no additional process requirements and environmental control requirements, and can be flexibly applied to the existing production line. Description of the Drawings

[0044] Figure 1 It is a schematic diagram of pore formation of the pole piece in the embodiment of the present application;

[0045] Figure 2 It is a cross-sectional schematic diagram of the porous structure in the embodiment of the present application;

[0046] Figure 3 It is a schematic diagram of the structure of the porous structure in the embodiment of the present application;

[0047] Figure 4 It is a schematic diagram of porous particles filled into the porous structure in the embodiment of the present application;

[0048] Figure 5 It is a cross-sectional schematic diagram of the porous particles in this embodiment;

[0049] Figure 6 It is a surface SEM morphology diagram of the negative pole piece after pore formation in the embodiment of the present application;

[0050] Figure 7Cross-sectional SEM morphology diagram of the negative electrode sheet after pore formation according to an embodiment of the present application;

[0051] Figure 8 Schematic curve diagram of the high-temperature storage capacity retention rate in this embodiment;

[0052] Figure 9 Schematic curve diagram of the fast charge cycle capacity retention rate in this embodiment.

[0053] Reference numerals:

[0054] 201, current collector; 202, active material layer; 301, porous structure; 401, porous particles; 501, pores; 601, lithium ions. Detailed implementation manners

[0055] The technical solutions of the present invention are further described below through specific embodiments. The specific embodiments do not represent a limitation on the protection scope of the present invention. Some non-essential modifications and adjustments made by others based on the concept of the present invention still fall within the protection scope of the present invention.

[0056] The "range" disclosed herein is defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of a particular range. The ranges defined in this way can include or not include the end values, and can be combined arbitrarily, that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, ranges of 60-110 and 80-120 are also contemplated. In addition, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are listed, the following ranges are all contemplated: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In the present disclosure, unless otherwise stated, the numerical range "a-b" represents an abbreviated representation of any real number combination between a and b, where a and b are both real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" have been fully listed herein, and "0-5" is only an abbreviated representation of these numerical combinations. In addition, when stating that a certain parameter is an integer ≥2, it is equivalent to disclosing that the parameter is, for example, the integer 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0057] In the present disclosure, unless otherwise specified, all the embodiments and preferred embodiments mentioned herein can be combined with each other to form a new technical solution.

[0058] In the present disclosure, unless otherwise specified, all the technical features and preferred features mentioned herein can be combined with each other to form a new technical solution.

[0059] Please refer to Figures 1 - 5 As shown, an electrode sheet provided by an embodiment of the present application includes a current collector 201 and an active material layer 202 compounded on the surface of the current collector 201; the active material layer 202 has a porous structure 301, and porous particles 401 are filled in the porous structure 301.

[0060] In the embodiment of the present application, by means of the porous particles 401 filled in the porous structure 301, the occurrence of side reactions is significantly reduced without deteriorating the kinetic performance, and the porous particles 401 are filled in the porous structure 301 of the active material layer 202. By using the porous particles 401, the stability of the porous structure 301 during charge and discharge is maintained, and at the same time, the wettability of the electrode sheet to the electrolyte can be improved, further enhancing the kinetic performance of the high coating weight electrode.

[0061] In some embodiments, the pore diameter R1 of the porous structure 301 is 10 - 500 μm, for example, it can be 10 μm, 15 μm, 50 μm, 100 μm, 150 μm, 200 μm, 250 μm, 300 μm, 350 μm, 400 μm, 450 μm, 500 μm, etc.; the pore spacing (distance between the edges of adjacent two pores) L1 of the porous structure 301 is 0.01 - 5 mm, for example, it can be 0.01 mm, 0.05 mm, 0.1 mm, 0.5 mm, 1.0 mm, 1.5 mm, 2.0 mm, 2.5 mm, 3.0 mm, 3.5 mm, 4.0 mm, 4.5 mm, 5.0 mm, etc. Further, the pore diameter R1 is 15 - 100 μm, and the pore spacing L1 is 0.05 - 2 mm.

[0062] In some embodiments, the relationship between the pore depth H1 of the porous structure 301 and the thickness H2 of the single-sided active material layer 202 is expressed as follows:

[0063]

[0064] In the formula, the parameter α is a coefficient related to the intrinsic properties of the active material, and its value is between 0.05 and 0.9; C1 is the maximum rate during the battery charging process, and C2 is the maximum rate during the battery discharging process.

[0065] In some embodiments, the relationship between the total opening area S1 of the porous structure 301 and the surface area S2 of the single-sided active material layer 202 is expressed as follows:

[0066]

[0067] Please refer to Figure 3 、 Figure 6 and Figure 7As shown, in some embodiments, the porous structure 301 is a blind hole. The arrangement of the porous structure 301 on the surface of the electrode sheet can be a parallel uniform distribution or an irregular random distribution. The pore morphology and cross-section of the porous structure 301 can be in the shapes of a cone, a frustum of a cone, a cylinder, a spherical crown, etc.

[0068] Please refer to Figure 4 and Figure 5 As shown, in some embodiments, the porous particles 401 are highly conductive ionic porous materials, selected from one or more combinations of porous alumina, porous silica, porous silicate, porous ceramics, and porous metal oxides. The highly conductive ionic porous materials have low impedance and good wettability to the electrolyte, can penetrate into the pores, are beneficial to lithium ion transport, and then can improve the wettability of the electrode sheet to the electrolyte, and further enhance the kinetic performance of the high coating weight electrode.

[0069] In some embodiments, the average diameter of the porous particles 401 is 0.5 - 5 μm, for example, it can be 0.5 μm, 1.0 μm, 1.5 μm, 2.0 μm, 2.5 μm, 3.0 μm, 3.5 μm, 4.0 μm, 4.5 μm, 5.0 μm, etc.

[0070] In some embodiments, pores 501 are provided inside the porous particles 401 for lithium ion 601 to transport. The average diameter of the pores 501 is 1 - 60 nm, for example, it can be 1 nm, 5 nm, 10 nm, 15 nm, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, 50 nm, 55 nm, 60 nm, etc. Further, the average diameter of the pores 501 is 1 - 40 nm.

[0071] The embodiment of the present application also provides a method for preparing an electrode sheet, including the following steps:

[0072] Step 1: Prepare a negative electrode active material slurry, coat the prepared negative electrode active material slurry on the surface of the negative electrode current collector, and dry it to prepare a negative electrode sheet, and then roll it;

[0073] Step 2: Prepare a positive electrode active material slurry, coat the prepared positive electrode active material slurry on the surface of the positive electrode current collector, and dry it to prepare a positive electrode sheet, and then roll it;

[0074] Step 3: Punch the prepared negative electrode sheet and positive electrode sheet to form a negative electrode sheet and a positive electrode sheet with a porous structure;

[0075] Step 4: Fill the porous particle slurry into the porous structures of the negative electrode sheet and the positive electrode sheet;

[0076] Step 5: Bake the negative electrode sheet and the positive electrode sheet to obtain an electrode sheet filled with porous particles.

[0077] In Step 1, the preparation of the negative electrode active material slurry includes the following: Based on 100% by mass, the first negative electrode active material, the second negative electrode active material, the first conductive agent, the second conductive agent, the first binder, and the first dispersant are added to water according to a mass ratio of (90 - 98):(0 - 5):(0.1 - 1.6):(0.1 - 1):(0.5 - 2):(0.7 - 2) and stirred evenly to obtain the negative electrode active material slurry. Preferably, the mass ratio is (91 - 97):(0 - 5):(0.1 - 1.2):(0.1 - 0.5):(1.0 - 1.8):(0.8 - 1.4). Among them, the first negative electrode active material can be at least one of graphite and hard carbon materials; the second negative electrode active material can be one or two combinations of silicon-carbon negative electrode materials and silicon-oxygen negative electrode materials; the first conductive agent and the second conductive agent can be one or more of acetylene black, conductive carbon black, carbon nanotubes, and graphene; the first binder can be one or more of polyvinylidene fluoride, polyacrylic acid, and styrene-butadiene rubber; the first dispersant can be one or more of sodium carboxymethyl cellulose and lithium carboxymethyl cellulose. The blending of the first negative electrode active material and the second negative electrode active material for the negative electrode active material and the blending of the first conductive agent and the second conductive agent for the conductive agent can be flexibly adjusted. For example, the negative electrode active material is blended with high-kinetic graphite and low-cost silicon-oxygen negative electrode materials; the conductive agent is blended with low-cost conductive carbon black and high-strength carbon nanotubes.

[0078] In Step 2, the preparation of the positive electrode active material slurry includes the following: Based on 100% by mass, the first positive electrode active material, the second positive electrode active material, the first conductive agent, the second conductive agent, and the first binder are added to N-methylpyrrolidone according to a mass ratio of (90 - 98):(0 - 5):(0.1 - 1.6):(0.1 - 1.6):(0.1 - 2) and stirred evenly to obtain the positive electrode active material slurry. Preferably, the mass ratio is (94 - 98):(0 - 3):(0.7 - 1.5):(0.7 - 1.5):(0.1 - 1.0). Among them, the first positive electrode active material and the second positive electrode active material can be one or more of lithium iron phosphate, lithium manganese iron phosphate, lithium cobalt oxide, lithium manganese oxide, lithium nickel cobalt manganese oxide, and lithium nickel cobalt aluminum oxide. The first conductive agent and the second conductive agent can be one or more of acetylene black, conductive carbon black, carbon nanotubes, and graphene; the first binder can be one or more of polyvinylidene fluoride, polyacrylic acid, and styrene-butadiene rubber. The blending of the first positive electrode active material and the second positive electrode active material for the positive electrode active material and the blending of the first conductive agent and the second conductive agent for the conductive agent can be flexibly adjusted. For example, the positive electrode active material is blended with high-stability lithium iron phosphate and low-cost lithium manganese oxide; the conductive agent is blended with low-cost conductive carbon black and high-strength carbon nanotubes.

[0079] The effects of the embodiments of the present application are described below through Examples 1-3 and Comparative Examples 1-2.

[0080] For the experimental methods without specific conditions noted in the following examples, they are generally carried out under conventional conditions or according to the conditions recommended by the manufacturer. The cell trial production conditions in this application refer to the temperature and air pressure in the daily operation room. In order to effectively compare the beneficial effects of the perforated electrode sheets, the parameters such as the material system, coating amount, compaction density, electrolyte, and pressure formation process in the following examples are uniformly specified, and only the influence of the surface porous electrode sheet on the battery performance is studied.

[0081] Example 1:

[0082] A kind of electrode sheet, preparation method and its application. The electrode sheet includes a positive electrode sheet and a negative electrode sheet with opposite polarities. The single-sided coating weight of the positive electrode sheet is 180 g / m 2 , and the single-sided coating weight of the negative electrode sheet is 83 g / m 2 . After the rolling process of the positive and negative electrode sheets, a porous structure is manufactured on the surface of the edge area of the electrode sheet by mechanical processing. The specific porous structure parameters are as follows:

[0083] The porous structure 301 of the negative electrode sheet is a conical blind hole. The pore diameter of the porous structure 301 is 30 μm, the pore depth of the porous structure 301 is 45 μm, the pore spacing of the porous structure 301 is 50 μm, the porous structure 301 is arranged parallel to the edge of the electrode sheet, and the total opening area of the porous structure 301 accounts for 23.4% of the surface area of the single-sided active material layer 202;

[0084] After the mechanical pore-making process of the negative electrode sheet, the porous inorganic alumina particle slurry is filled into the porous structure 301 by the gravure roll coating method, and then dried by baking to obtain a porous negative electrode sheet filled with porous inorganic alumina particles; the average diameter of the porous inorganic alumina particles is 5 μm; the average diameter of the internal pores of the porous inorganic alumina particles is 30 nm;

[0085] The positive electrode sheet and the negative electrode sheet are cut into single sheets by the die-cutting process, and the positive electrode sheet, the negative electrode sheet, and the separator are stacked in sequence through the Z-shaped lamination process to assemble a laminated electrode core; through the hot pressing process, the positive electrode sheet, the negative electrode sheet, and the separator are bonded together. Through the assembly process, the laminated electrode core is sealed into an aluminum shell body, and then through processes such as liquid injection, formation, aging, and grading, a laminated square aluminum cell is prepared.

[0086] Example 2:

[0087] A kind of electrode sheet, preparation method and its application. The electrode sheet includes a positive electrode sheet and a negative electrode sheet with opposite polarities. The single-sided coating weight of the positive electrode sheet is 180 g / m 2 , and the single-sided coating weight of the negative electrode sheet is 83 g / m2 After the positive and negative electrode plates are roll-pressed, a porous structure is fabricated on the surface of the edge region of the electrode plate by mechanical machining. The specific porous structure parameters are as follows:

[0088] The porous structure 301 of the negative electrode plate is a conical blind hole. The pore diameter of the porous structure 301 is 30 μm, the pore depth of the porous structure 301 is 45 μm, the pore spacing of the porous structure 301 is 50 μm, the porous structure 301 is arranged parallel to the edge of the electrode plate, and the total opening area of the porous structure 301 accounts for 23.4% of the surface area of the single-sided active material layer 202;

[0089] After the mechanical pore-forming process of the negative electrode plate, the porous ceramic particle slurry is filled into the porous structure 301, and then dried by baking to obtain a porous negative electrode plate filled with porous ceramic particles; the average diameter of the porous ceramic particles is 3 μm; the average diameter of the internal pores of the porous ceramic particles is 50 nm;

[0090] The positive and negative electrode plates are cut into single sheets by die-cutting. Through the Z-shaped laminating process, the positive electrode plate, the negative electrode plate, and the separator are stacked in sequence to assemble a laminated electrode core; through the hot-pressing process, the positive electrode plate, the negative electrode plate, and the separator are bonded together. Through the assembly process, the laminated electrode core is sealed into an aluminum shell, and then through processes such as liquid injection, formation, aging, and grading, a laminated square aluminum battery cell is prepared.

[0091] Example 3:

[0092] An electrode plate, a preparation method and its application. The electrode plate includes a positive electrode plate and a negative electrode plate with opposite polarities. The single-sided coating weight of the positive electrode plate is 180 g / m 2 , and the single-sided coating weight of the negative electrode plate is 83 g / m 2 . After the positive and negative electrode plates are roll-pressed, a porous structure is fabricated on the surface of the edge region of the electrode plate by mechanical machining. The specific porous structure parameters are as follows:

[0093] The porous structure 301 of the negative electrode plate is a round-headed column blind hole. The pore diameter of the porous structure 301 is 30 μm, the pore depth of the porous structure 301 is 60 μm, the pore spacing of the porous structure 301 is 40 μm, the porous structure 301 is arranged parallel to the edge of the electrode plate, and the total opening area of the porous structure 301 accounts for 28.3% of the surface area of the single-sided active material layer 202;

[0094] After the mechanical pore-forming process of the negative electrode plate, the porous ceramic particle slurry is filled into the porous structure, and then dried by baking to obtain a porous negative electrode plate filled with porous ceramic particles; the average diameter of the porous ceramic particles is 3.5 μm; the average diameter of the internal pores of the porous ceramic particles is 60 nm;

[0095] The positive electrode plate and the negative electrode plate are cut into single-piece electrode plates through a die-cutting process. Through a zigzag stacking process, the positive electrode plate, the negative electrode plate, and the separator are stacked in sequence to assemble a stacked electrode core. Through a hot pressing process, the positive electrode plate, the negative electrode plate, and the separator are bonded together. Through an assembly process, the stacked electrode core is sealed into an aluminum shell body, and then through processes such as liquid injection, formation, aging, and grading, a stacked square aluminum battery cell is prepared.

[0096] To highlight the beneficial effects of this application, the following comparative examples are set for the embodiments:

[0097] Comparative Example 1:

[0098] An electrode plate, a preparation method and its application, the electrode plate includes a positive electrode plate and a negative electrode plate with opposite polarities. The single-sided coating weight of the positive electrode plate is 180 g / m 2 , and the single-sided coating weight of the negative electrode plate is 83 g / m 2 . After the positive and negative electrode plates are roll-pressed, the electrode plates are cut into single-piece electrode plates through a die-cutting process. Through a zigzag stacking process, the positive electrode plate, the negative electrode plate, and the separator are stacked in sequence to assemble a stacked electrode core. Through a hot pressing process, the positive electrode plate, the negative electrode plate, and the separator are bonded together. Through an assembly process, the stacked electrode core is sealed into an aluminum shell body, and then through processes such as liquid injection, formation, aging, and grading, a stacked square aluminum battery cell is prepared.

[0099] Comparative Example 2:

[0100] An electrode plate, a preparation method and its application, the electrode plate includes a positive electrode plate and a negative electrode plate with opposite polarities. The single-sided coating weight of the positive electrode plate is 180 g / m 2 , and the single-sided coating weight of the negative electrode plate is 83 g / m 2 . After the positive and negative electrode plates are roll-pressed, a porous structure is manufactured on the surface of the edge region of the electrode plate by mechanical processing. The specific porous structure parameters are as follows:

[0101] The porous structure 301 of the negative electrode plate is a conical blind hole. The hole diameter of the porous structure 301 is 25 μm, the hole depth of the porous structure 301 is 45 μm, the hole spacing of the porous structure 301 is 50 μm. The porous structure 301 is arranged parallel to the edge of the electrode plate, and the total opening area of the porous structure 301 accounts for 20% of the surface area of the single-sided active material layer 202.

[0102] The positive electrode pole piece and the negative electrode pole piece are cut into single-piece pole pieces through a die-cutting process. Through a Z-shaped stacking process, the positive electrode pole piece, the negative electrode pole piece, and the separator are stacked in sequence to assemble a stacked pole core. Through a hot pressing process, the positive electrode pole piece, the negative electrode pole piece, and the separator are bonded together. Through an assembly process, the stacked pole core is sealed into an aluminum shell body, and then through processes such as liquid injection, formation, aging, and grading, a stacked square aluminum battery cell is prepared.

[0103] The batteries prepared in Example 1, Example 2, Comparative Example 1, and Comparative Example 2 were fully charged to 100% SOC, then stored and aged at 45°C, and the capacity was restored every 28 days for a total storage of 140 days. The high-temperature storage results are as Figure 8 shown: The high-temperature storage capacity retention rate of Comparative Example 1 is 84.3%, the high-temperature storage capacity retention rate of Comparative Example 2 is 81.6%, the high-temperature storage capacity retention rate of Example 1 is 86.1%, and the high-temperature storage capacity retention rate of Example 2 is 85.4%. From the above comparison, it can be seen that the combination of pole piece pore formation and optimization of the porous structure design in this application can improve the high-temperature storage capacity retention rate and improve the storage performance of the electrode pole piece.

[0104] The batteries prepared in Comparative Example 1, Comparative Example 2, and Example 3 were subjected to a fast charge and discharge cycle test. The upper limit voltage (Vmax) of the cycle range was 3.65V, and the lower limit voltage was 2.0V. The cycle steps were as follows: At 25°C, charge at a 3C rate to the cut-off SOC and let it stand for 1h; then discharge at a 1C rate at a constant current to the cut-off voltage (2.0V) and let it stand for 1h. The above charge and discharge process was cycled 900 times. The 25°C fast charge and discharge cycle results are as Figure 9 shown: The cycle capacity retention rate of Comparative Example 1 is 89%, the capacity retention rate of Comparative Example 2 is 92%, and the capacity retention rate of Example 3 is 94%. From the above comparison, it can be seen that the combination of pole piece pore formation and optimization of the porous structure design in this application can improve the fast charge and discharge cycle capacity retention rate and improve the kinetic performance of the electrode pole piece.

[0105] After the fast charge and discharge cycle of the battery, it was fully charged and disassembled to observe the lithium deposition state in different regions of the fully charged negative electrode pole piece, as shown in Table 1 below:

[0106] The degree of lithium deposition at the fully charged negative electrode interface is defined as follows:

[0107] 0: No lithium deposition can be observed with the naked eye;

[0108] 1: Trace lithium deposition (the lithium deposition area is less than 5% of the active material layer area of the corresponding region);

[0109] 2: Small-area lithium deposition (the lithium deposition area is 5-20% of the active material layer area of the corresponding region, excluding the case of equal to 20%);

[0110] 3: Large-area lithium deposition (the lithium deposition area is 20-50% of the area of the active material layer in the corresponding region);

[0111] 4: Large-area lithium deposition (the lithium deposition area is greater than 50% of the area of the active material layer in the corresponding region).

[0112] Table 1 Lithium deposition degree of the negative electrode sheet

[0113]

[0114] According to the results presented in Table 1 above, it can be seen that the lithium deposition degree in the lithium intercalation region of the negative electrode sheet in Example 3 is zero in the edge region of the sheet and also zero in the center region of the large area of the sheet. That is to say, by adopting the method of Example 3, the high coating weight electrode is not prone to lithium deposition problems during high-rate charge and discharge, making the battery monomer relatively safe during long-term use.

[0115] The above are only the preferred embodiments of the present application and are not used to limit the present application. For those skilled in the art, various changes and modifications can be made to the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included within the protection scope of the present application.

Claims

1. A pole piece, characterized in that, Comprising: a current collector and an active material layer composite on the surface of the current collector; the active material layer has a porous structure, and the porous structure is filled with porous particles.

2. The electrode sheet according to claim 1, wherein the pore diameter R1 of the porous structure is 10 to 500 μm; the pore spacing L1 of the porous structure is 0.01 to 5 mm.

3. The electrode sheet according to claim 1, wherein the relationship between the pore depth H1 of the porous structure and the thickness H2 of the single-sided active material layer is expressed as follows: In the formula, the parameter α is a coefficient related to the intrinsic properties of the active material, and its value is between 0.05 and 0.9; C1 is the maximum rate during battery charging, and C2 is the maximum rate during battery discharging.

4. The electrode sheet according to claim 1, wherein the relationship between the total opening area S1 of the porous structure and the surface area S2 of the single-sided active material layer is expressed as follows:

5. The electrode sheet according to claim 1, wherein the porous particles are selected from one or more combinations of porous alumina, porous silica, porous silicate, porous ceramics, and porous metal oxides.

6. The electrode sheet according to claim 1, wherein the average diameter of the porous particles is 0.5 to 5 μm; pores are provided inside the porous particles, and the average diameter of the pores is 1 to 60 nm.

7. A method for preparing a pole piece according to any one of claims 1 to 6, characterized in that, Including the following steps: Preparing a negative electrode active material slurry, coating the prepared negative electrode active material slurry on the surface of a negative electrode current collector, and drying to prepare a negative electrode sheet, and then performing rolling; Preparing a positive electrode active material slurry, coating the prepared positive electrode active material slurry on the surface of a positive electrode current collector, and drying to prepare a positive electrode sheet, and then performing rolling; Performing a punching treatment on the prepared negative electrode sheet and positive electrode sheet to form the negative electrode sheet and positive electrode sheet having a porous structure; Filling a porous particle slurry into the porous structures of the negative electrode sheet and the positive electrode sheet; Baking the negative electrode sheet and the positive electrode sheet to obtain an electrode sheet filled with porous particles.

8. The preparation method according to claim 7, wherein the preparation of the negative electrode active material slurry includes: adding a first negative electrode active material, a second negative electrode active material, a first conductive agent, a second conductive agent, a first binder, and a first dispersant in a mass ratio of (90 - 98):(0 - 5):(0.1 - 1.6):(0.1 - 1):(0.5 - 2):(0.7 - 2) to water and stirring evenly; and / or the preparation of the positive electrode active material slurry includes: adding a first positive electrode active material, a second positive electrode active material, a first conductive agent, a second conductive agent, and a first binder in a mass ratio of (90 - 98):(0 - 5):(0.1 - 1.6):(0.1 - 1.6):(0.1 - 2) to N-methylpyrrolidone and stirring evenly.

9. The preparation method according to claim 8, wherein the first negative electrode active material is at least one of graphite and hard carbon materials; The second negative electrode active material is one or two compositions of a silicon-carbon negative electrode material and a silicon-oxygen negative electrode material; The first positive electrode active material and the second positive electrode active material are one or more of lithium iron phosphate, lithium manganese iron phosphate, lithium cobaltate, lithium manganate, lithium nickel cobalt manganate, and lithium nickel cobalt aluminate; The first conductive agent and the second conductive agent are one or more of acetylene black, conductive carbon black, carbon nanotubes, and graphene; The first binder is one or more of polyvinylidene fluoride, polyacrylic acid, and styrene-butadiene rubber; The first dispersant is one or more of sodium carboxymethyl cellulose and lithium carboxymethyl cellulose.

10. A battery, characterized in that, It includes the electrode sheet described in any one of claims 1-6 or the electrode sheet prepared by the preparation method of the electrode sheet described in any one of claims 7-9.

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